You need at least 2 files (ov2 and bmp) for each data collection. Ogg and _x2.bmp are optional and may not work on some old TomTom models.
All files must have the same file name, for example:
SpeedCamera.ov2 - the data file
SpeedCamera.bmp - the standard 22x22 pixels icon
SpeedCamera.ogg - the sound in 22050 Hz mono converted into an ogg audio file
SpeedCamera_X2.bmp - the large popup alert
How to install TomTom POI files:
1. Connect the TomTom with the USB cable and turn it on. Do not use TomTom Home.
2. Open 'My Computer' and tind the TomTom sign labeled as 'TomTom'. Alternatively you could copy all downloaded POI updates directly into an SD card using any SD reader (faster and more reliable).
3. Open the TomTom drive by double clicking on it or click 'Explore'. Find TomTom map folder. It's name may look like: Western_Europe-Map, United Kingdom and Republic of Ireland, Great_Britain-Map, United States, Australia, Western_Europe-Map, etc.
4. Copy all saved files to the map folder: Select the downloaded POI updates by clicking on them and press CTRL C. Navigate to the map folder that you located above and press CTRL V. This will copy the files to the map directory on the TomTom. You may use any alternative, e.g. drag and drop these POIs across.
5. Enable the new installed POI files that has just been copied across: Disconnect your GPS from your computer and turn on the TomTom.
Goto: Change Preferences --> Manage/Maintain POI --> Enable / Disable POI and select/deselect your new extra POIs.